COAT platelet defect

A collagen- and thrombin-activated (COAT) platelet defect is a platelet function disorder that is due to a reduced ability to generate procoagulant platelets. It is associated with a clinically relevant bleeding phenotype.

During physiological platelet activation, a fraction of platelets expresses phosphatidylserine on their surface and become highly efficient in sustaining thrombin generation. These so-called COAT platelets, can be generated by dual-agonist stimulation with collagen and thrombin in a laboratory setting. COAT platelet defects should be distinguished from Scott syndrome, a rare bleeding disorder in which patients have impaired phospholipid scrambling and do not express negatively charged phospholipids on their surface even after treatment with calcium ionophores.